A shock absorber, or a damper, is utilized for reducing an impact force applied to a moving member when stopping the moving member at a movement end position.
A hydraulic damper described in Japanese Unexamined Patent Application Publication No. H06-346938 has an outer case in which oil is filled and a damper case disposed inside the outer case, and a passage through which oil flows is formed between the outer case and the damper case. A piston is disposed inside the damper case and is reciprocable in an axial direction of the damper case, and a piston rod attached to the piston protrudes to the outside from a proximal end portion of the outer case. When a moving member collides with a proximal end of the piston rod, oil inside a rear-side chamber flows from an orifice formed on a bottom portion of the damper case, through the passage, and to a front-side chamber. At this time, a passing resistance of the oil is applied to the piston as a drag force, kinetic energy of the moving member is absorbed by this drag force of the oil, and thus, an impact force applied to the moving member is reduced. In order to adjust a drag characteristic, or a damping characteristic, of the damper, a needle shaft for changing a flow rate of oil flowing from the orifice to the passage is provided on a rear wall of the outer case, and the needle shaft is fixed to the rear wall with a nut.
A fluid pressure damper described in Japanese Unexamined Utility Model (Registration) Application Publication No. H06-37641 has a reservoir tube serving as an outer case and a pressure tube installed inside the reservoir tube, and a throttle hole through which pressurized oil inside the pressure tube flows out is formed on an inner cover of the pressure tube. In order to adjust a damping characteristic, an eccentric cam for changing the size of an opening of the throttle hole is provided on a bottom portion of the reservoir tube, and the eccentric cam is fixed to the reservoir tube with a locking screw.
A hydraulic damper for damping vehicle vibration is described in Japanese Unexamined Patent Application Publication No. H07-103279, and a compression coil spring is disposed on an outside portion of the hydraulic damper. This hydraulic damper has an outer cylinder and an inner cylinder, a piston is disposed inside the inner cylinder and is reciprocable in an axial direction of the inner cylinder, and a piston rod attached to the piston protrudes to the outside. A reservoir chamber formed between the outer cylinder and the inner cylinder communicates with a rod-side oil chamber formed inside the inner cylinder through an orifice passage formed on the inner cylinder, a rod guide main body for adjusting a communication opening degree of the orifice passage is fitted to the inner cylinder, and a plurality of orifices are formed on the rod guide main body. A rotation angle of the rod guide main body is regulated by the rotation regulating pin.